On the slab before the first course goes down, you find out very quickly who drew the plan to the material and who just drafted a neat number on a screen. Stop dimensioning masonry rooms to round figures like 4.00m or 3.50m. Take the exact unit size of your block—whether it’s local tufo or standard poroton—add the 10mm mortar joint, and set the clear opening to 4.07m or 3.56m. You eliminate the off-cuts, keep the bond pattern unbroken at every reveal, and save days of angle-grinder dust. It’s the simplest way to prove to a site foreman that you actually understand how a wall stands up.